Apparatus for laminating thermoplastic film sheets



Oct. 22, 1957 M. o. LONGSTRETH EIAL 2,

' APPARATUS FOR LAMINATING THERMOPLASTIC FILM SHEETS Filed May 2, 1955 2Sheets-Sheet 2 IN V EN TORS Murray 0. Langs/re/A By GMber/ .J Ward ATTORNE rs United States, atemo" APPARATUS FOR LAMINATING THERMOPLASTICFILM SHEETS Murrey 0. Longstreth and Gilbert J. Ward, Midland,

Mich assignors to The Dow Chemical Company, Midland, Mich., acorporation of Delaware Application May 2, 1955, Serial No. 505,296

1 Claim. (Cl. 154-1) laminated together to take advantage of the mostdesirable characteristics and properties of each. The properties of thelaminated article are frequently greater than the sum of the propertiesof the individual sheets. In previous methods of laminating sheets thesheets were pressed together either hot, to cause a fusion betweensheets, or by means of an adhesive. When a thin oriented sheet washeat-laminated to a relatively thick unoriented sheet the heat wouldshrink the oriented film, causing an uneven surface to be formed on thelaminate. When it was attempted to laminate two sheets under conditionssuch that there would be no shrinkage, it was impossible to remove allthe wrinkles, and other unevenness from the film, so that a roughsurface was again produced. Frequently, the very problem that was to besolved by lamination was the elimination of a matte or uneven surface,and consequently the prior methods of lamination did not achieve thedesired result.

An object is the provision of a laminating apparatus capable ofcontinuous operation and which may be employed in conjunction with athermoplastic sheet-producing apparatus.

The above and related objects are achieved with a process comprising thesteps of supplying a hot unoriented sheet of thermoplastic materialbetween the nip of two smooth pressure rolls, at least one of which isheated, and supplying an oriented thermoplastic film sheet compatiblewith the other about the heated roll, while holding the edges of thefilm under tension, and into pressure contact with the first sheet atthe nip between the two rolls. The heated roll shrinks the orientedsheet only to the extent of removing any wrinkles and slack portions ofthe film. Since the edges of the sheet are restrained, the film does notshrink out of size but retains its original size. Thus, when the heatedfilm is brought into contact with the unoriented sheet the film issmooth and taut, and the surface of the resulting laminate is likewisesmooth and polished.

It is preferred to heat both rolls to insure a more uniform and completefusion of the sheets. It is also preferred to employ at least a 3-rollcalender stack and to pass the laminated sheet successively through theseveral nips between the rolls. In this way the laminated sheet is keptin contact with the rolls long enough to aid in setting the interface ofthe laminate.

The processs will be more readily understood from the drawing andfollowing descripton of the apparatus which may be used for carrying outthe process. In the drawings,

2,810,423 Patented Oct. 22, 1957 ice,

Fig. 1 is afront elevation of a preferred apparatus;

Fig. 2 is a planet the apparatus;

Fig. 3 is a cross-section along line 3-3 of Fig. 1;

Fig. 4 is a viewtaken alongline 4'-4 of Fig. 1, showing the means fordriving the rolls; and,

Fig. 5 is a diagrammatic sketch of the apparatus e ployed in conjunctionwith a sheet extruder.

In the illustrated embodiment a supporting frame is provided with a bedand two upright members 11 for supporting the working members of theapparatus. Three rolls 12, 13, 14 are. supported horizontally on shafts15, 16, 17 extending through bearings in the upright members 11. Therolls 12, 13, 14 are positioned in pressure relationship to have anarrow nip 18, 19' between each pair. The rolls 12, 13, 14 may beprovided with heating or cooling means. As illustrated, the rolls 12,13, 14 and shafts 15, 16, 17. are hollow, so that heat transfer fluidsmay be passed therethrough. At the end of each shaft 15, 16, 17 is arotatable seal 20 in conjunction with a union 21. The union 21 in turnis connected to a flexible hose 22 which leads to a supply of heattransfer fluids.

Companion grooves 25, 26 are provided about the periphery of the twoupper rolls 12, 13 near the roll ends. Each groove 25 in the upper roll12 is in vertical alignment with a corresponding groove 26 in theadjacent roll 13.

Extending backward and upward angularly from the back edge of eachsupporting member 11 and integral therewith and at approximately thesame height as the upper roll 12 is a projection 27 of the supportingmember 11 (Fig. 3). In the illustrated embodiment each such projectionconsists of two arms 27 to the ends of which are bolted split bearings28. Extending through the bearings 28 is a shaft 29 which acts as a corefor a roll of film 30.

Fastened to the upper part of each supporting member 11 is a bracket 32(Fig. 2), extending over the upper roll 12 so that at the rearward edgeof the bracket 32, the extremity of its lower surface 33 is at lowerlevel than the upper line of the roll 12. The lower rearward ends ofbrackets 32 support the ends of a horizontal shaft 34 at a levelslightly below that of the upper line of the upper roll 12. The shaft 34is preferably freely rotatable and serves as a guide and tension rollfor thin film sheets. However, it may be fixed and highly polished sothat the film may slip past it.

Located directly above the shaft 34 is a rotatable horizontal shaft 35extending through bearings in the brackets 32, carrying two sheaves 36mounted in the same vertical planes as the grooves 25, 26 in the uppertwo rolls 12, 13. I

Attached on the inner side of each bracket 32 is a generally triangulartension adjusting plate 37, pivoted near its apex about a bolt 38located in the vertical plane tangent to the rear side of the rolls 12,13, 14. Curved slots 39 are cut into the forward edge of the plate 37through which bolts 40 are inserted into threaded holes in the bracket32. The plate 37 can thus be pivoted up or down a distance equal to thelength of the slots 39 and locked in a fixed position. Welded near theforward edge of each plate 37 is a boss 41 into which is inserted ajackshaft 42. Mounted on a freely rotating bearing 43 keyed to thejackshaft 42 is a sheave 44. Each sheave 44 is in the same verticalplane as one of the grooves 25, 26 in the rolls 12, 13 and sheave 36. Anendless cable 45 is passed over and around first sheave 36 then alongthe groove 25 in the upper roll 12, through the nip 18 between the uppertwo rolls 12, 13, along the groove 26 in the opposite side of the middleroll 13, and through the nip 19 between the lower two rolls 13, 14. Thecable 45 then passes over and around the second" sheave44-fromswhereit-=returns to the first-sheave 36 To move the sheets offilm andth'e cabl tlie rolls 12', 13, 14 are driven at approximately thesame speed. Any. suitable. drive=mechanism.:may;, bedemployedm ln theillustrated embodiment (Big; 4)} alpiniomggar; 46 is keyedyto. the drive..end-of,'each.of the. shafts 15,.v 16, 17. Meshedwith eaehofi thegearsv46iis=a .worm .gear 47 mounted on averticalfdriveshaft .48., Thevdrive: shaft 48 is mountedinibearing's. 49, carried biy upright member11. Keyedito ,the. lower. endofdriveshaft 48.1is.

adriven gear. 50.. which. is. meshed with. a worm. gear SLmountedQonadriven vslziaftsuch as that ofimotonSL. A .means for supplying,the..base.. sheet .53.. of. thermoplastic. material, to be. laminatedmust .be provided. AS

convenient .means..for providingnhecbase :slieeti853 sheet expressingextruders 5.4;- In. this, way separate.v storing and handling operationsare.eliminated. and a,ho.t.sheet suitable. fort laminatingoperationsrist provided. directly,

Such an arrangements, is illustrateddiagrammatically, in

Figure 5.1

In operation, atoll. 30; ofl orientedLfiIm.isnmountcd.

on. shaft 29 in. split-bearings .28.. The free end of the film 55 :is.fed oven roll :12 with the edgessgrippedbycable 45L A .hot unoriented:sheet .53 is. fed. into. nip. 1% between rolls 12 and 13 between cables.45.- Roll 12,.is...

heatedand roll13..is cooled tosetthe fusedlaminated interface... As$11.12 rotates the..fihn.55.'is,:brought:into, contact with the-vunorientedt sheet; 53 at; nip. 18.. The: pressure exerted by;rol-ls..12and' 13 .and.the .heat'spresent. The:

causes the two sheets to be laminated by fusion. laminated. sheet. 56is. then. passed. around.- rollv. 13. into the. nip 19 between. rolls.13. and.14 from whichpoint.

it' is carriedaway, frornthe apparatus.

In .actual. operation, an unorientedi sheet 53 s was. ex!

truded froma composition-of polystyrene;andr=pereentv GRS synthetic.rubber.v The unoriented. sheetv had? a. matte finish after: extrusion.This sheetwaslaminated, by means. ofv the:-p,rocess 0ft this invention;to. a; highlyglossy oriented film of polystyrene and. the: resulting.

ented; comprising a-istackzofia ileastth-reedriven; calender."

rolls, an adjacent: pairroft rolls-of. said. stack havingcircumferentiah: grooves neanteachtend of. each-2 of: said rolls, the.grooves. in adjacentsrolls being in.the same vertical plane; two pairsofsh'eavesmounted "above said stack and with onmmemberzofeaclipair oneach side of said stack and in the plane through one of said grooves;and endless cable extending about one of the sheaves ofeach pair.thence. over: and half, aroundhthe outer. roll of. the i groovedpair-,gsaid; cable lying; in the:

groove thereom. thence through the nip between the grooved rolls,.halftaround the. other grooved roll,- thence 1 around. the-:second;sheave: and. returning; to the first sheave; :means for. supplyinghot-.unoriented plastic sheet to.the.nip between ;the grooved rolls andmeansforsup-- plying orientedplastio film of; a. width. greaterthanthew. distance betweensaid. grooves over: the outer. grooved.

roll {and-under, the. saidendless .cablest ReferencessCited in thefile.of this :patent UNITED STATES- PATENTS 13835267 Bscobales June.28, 1921,1,913,330 Bricliman .June,6, 1933. 1,998I866 Fowler. Apr...23-, 1935.]2,397,838.. Chavanncs Apr. 2, 1946.- 2,429, 1.77 Young; Oct 14,- 19472,434,541: Bierer Jam. 13; 19.483 2,-594,-229 Snyder.- etiali. ..Apr-..22, 1952!. 2,690,596: Gouldingzlr; etxalLI. OctaS'; 19541

